1. Field of the Invention
This invention relates to an electromagnetic wave energy conversion heat-generating material, a heating container for a microwave oven, and also a microwave oven. More particularly, it relates to an electromagnetic wave energy conversion heat-generating material, a heating container for a microwave oven, and also a microwave oven, all having a very high heat conversion efficiency and a superior durability.
2. Description of the Prior Art
Electromagnetic wave energy conversion heat-generating materials include those in which dielectric loss or magnetic loss is utilized and those in which a resistance material is utilized. Of these, ferrite-type heat-generating materials have been commonly used as the heat-generating materials that utilize the magnetic loss. On the other hand, the heat-generating materials comprising a resistance material have been often used in view of their heat generation efficiency, lightness in weight, cost, etc.
As specific resistance materials, carbon types (powder, fibers, whiskers, sinters, etc.) are most widely used. In these days, however, studies have been made on silicon carbide types (fibers, whiskers, powder, sinters, etc.), or materials comprising insulating fibers or whiskers (such as potassium titanate whiskers) whose particle surfaces have been made conductive (by reduction or by coating with a conductive substance), as well as conductive metal oxides (powder, sinters, etc.) such as conductive zinc oxide.
The carbon-type heat-generating materials, however, are disadvantageous in that the oxidation of carbon proceeds to become subject to combustion, and hence have been questioned on their safety and durability.
The silicon carbide types are expensive and have problems on the stability on heat generation. The conductive zinc oxide also have problems on heat generation efficiency.
The materials whose particle surfaces have been made conductive are commonly involved in the problem that the heat generation performance is deteriorated with time.